Trunking or link aggregation is a scheme for incrementally increasing the bandwidth of a point-to-point link by treating a group of parallel links as a single logical link. The IEEE 802.3ad standard guarantees that frames are received in the correct order by requiring that all frames in a single conversation travelling in the same direction be transmitted over the same link (or logical link).
A conversation may be defined as a sequence of frames that must be delivered in order. Some conventional techniques consider all frames that include the same combination of media access control (MAC) source address and destination address as being included in the same conversation. A problem with using MAC addresses to discriminate between conversations is that if a trunk is established between two routers, most of the traffic in one direction would have the same combination of MAC source and destination addresses.
Conventional network switches use trunking distribution schemes to determine which link in a trunk a particular frame of a conversation will be sent over. Some schemes try to evenly distribute traffic over the individual links of a trunk and others bias the traffic distribution such that high priority frames are transmitted over lightly used links. Conventional trunking distribution schemes, such as schemes that use the MAC source and destination addresses to distribute traffic over links of a trunk, however, typically result in an uneven distribution.